First Layer Settings, Height, Width etc question

[Grifftech]

petg tend to be a little stringy. prints will usually have alot of micro fine hairs. this can be normal. all you do is blow the part with a heat gun or run a lighter or flame quickly over the part and they disappear. i dont notice too many thing really over the top with your profile. if your filament dia is correct then your multiplier seems a bit high but that can vary printer to printer. mine is at 98. i assume you have run a thin wall calibration to dial that multiplier in? if your overextruding that will increase the stringing from the extra psi in the nozzle. 255 is ok for the temp but try dropping that to 245 and see what that does for you. again that can vary from printer to printer as well. i never used a bowden so i cant really comment on your retraction but overall it should be similar settings to your abs profile. couple of other things is your speeds seem a little odd. print speed can be up toward the 3600-3800 range. xy movement speed could be a little snappier as well. 9000-12000 maybe. these speed will vary also from printer to printer but yours just seem extremely low. the other thing is those first layer settings. man for a .2mm height those are pretty extreme. i could easily see if you increase your speed that you will never be able to extrude that amount of material without stripping the filament or jamming the extruder. at a .2mm layer height there is no reason to have that higher than 100%. the width maybe 100-125% or so. if that width is greater than the little flat spot on the tip of the nozzle you are just going to make a mess. a first layer like that is completely unnecessary.

Thank you, I will try your changes out. This might be why I am running into skipping issues with the extruder since it can't feed the filament fast enough.

[Grifftech]

petg tend to be a little stringy. prints will usually have alot of micro fine hairs. this can be normal. all you do is blow the part with a heat gun or run a lighter or flame quickly over the part and they disappear. i dont notice too many thing really over the top with your profile. if your filament dia is correct then your multiplier seems a bit high but that can vary printer to printer. mine is at 98. i assume you have run a thin wall calibration to dial that multiplier in? if your overextruding that will increase the stringing from the extra psi in the nozzle. 255 is ok for the temp but try dropping that to 245 and see what that does for you. again that can vary from printer to printer as well. i never used a bowden so i cant really comment on your retraction but overall it should be similar settings to your abs profile. couple of other things is your speeds seem a little odd. print speed can be up toward the 3600-3800 range. xy movement speed could be a little snappier as well. 9000-12000 maybe. these speed will vary also from printer to printer but yours just seem extremely low. the other thing is those first layer settings. man for a .2mm height those are pretty extreme. i could easily see if you increase your speed that you will never be able to extrude that amount of material without stripping the filament or jamming the extruder. at a .2mm layer height there is no reason to have that higher than 100%. the width maybe 100-125% or so. if that width is greater than the little flat spot on the tip of the nozzle you are just going to make a mess. a first layer like that is completely unnecessary.

Haven't heard of Thin Wall Calibration so I should probably look into that Have any good reference material on it?

[jimc]

here you go. this is a very good thread on extrusion calibration.


http://forum.makergear.com/viewtopic.php?f=3&t=1964

[dcameron]

You can figure it out pretty easily by looking through the gcode. My raft with default settings prints around 220% height, 200% width, and nice and slow to make sure it sticks. That's using default medium settings with 0.4mm nozzle and 0.2mm layer heights. I imagine that if you are printing at a lower layer height like 0.1mm, the first layer height would actually be double that (closer to 400%) as that would equate to the same thickness.

Why do the raft settings do this? I have a layer height of .2mm but the print starts out at .45mm when I have a raft enabled. This does not make any sense to me because (from my experience) the closer the nozzle is to the bed initially, the better the part sticks. I would think that the raft settings would make the initial layer height less than the .2mm that I have it set at, not more.

[JoeJ]

You can still modify the "first layer height" setting and that will still have an affect on the first layer of the raft. For example, if you want to squish the first layer and print it at a 80% height, you can still do that.

Even though the raft is printed at a 0.45mm layer height, it extrudes more plastic to make up for it. In my experience, these thicker extrusions tend to stick MUCH better to the bed versus the tiny thin extrusions that are normally used.

[Rebekah_harper]

just had a thought. if you haven't resolved it yet.

it could well be that you need to dial down the extrusion multiplier. I've had it that it's trying to extrude more than the space allows. causing some back pressure. I don't think your nozzle is clogged but that it's just not able to put out as much as you are asking it to do.

if you dial it down to like 0.85 and see if it still happens. it's extreme put if it's lasting longer than before then you know the problem. if it does it again then there might be a temp issue where the material is turning into a powder like PVA does when it's too high. but I found that it calls for a nozzle replacement.

I strongly believe its the former.

give it a go and see what happens if it works then dial it up until you get the results.

let us know how it goes.

Becky

[BaronWilliams]

You can figure it out pretty easily by looking through the gcode. My raft with default settings prints around 220% height, 200% width, and nice and slow to make sure it sticks. That's using default medium settings with 0.4mm nozzle and 0.2mm layer heights. I imagine that if you are printing at a lower layer height like 0.1mm, the first layer height would actually be double that (closer to 400%) as that would equate to the same thickness.

Why do the raft settings do this? I have a layer height of .2mm but the print starts out at .45mm when I have a raft enabled. This does not make any sense to me because (from my experience) the closer the nozzle is to the bed initially, the better the part sticks. I would think that the raft settings would make the initial layer height less than the .2mm that I have it set at, not more.

Raft base layers work well because they print slow and wide.

A raft base layer usually prints with a width that's 2x your nozzle width, and a height that's 1.25x your nozzle width. For a 0.4mm nozzle this is usually about 0.80x0.50mm. The ratio is 1.6 times wider than it is high. This is a good ratio. However, with the nozzle printing this much filament very slowly, the side walls of each line tend to droop down, making more of the line touch the build platform than it normally would if printing less plastic per line. The droop is beneficial. The extruded lines droop more when a lot of plastic is extruded. The more it droops, the better the adhesion, because a larger percentage of the plastic is touching the build surface when it droops.

Rafts are printed wide, but also usually printed a bit high to help solve leveling problems. If your build plate is very level, you don't need to print the first layer wide and a little high.

For example, printing at 1.20x0.20mm will give very good adhesion, because the ratio is 6 times wider that it is high, so a very large percent of the plastic is touching the build surface. But if your build plate isn't very level, you want a layer height that's higher than 0.20mm or you will have problems.

The key to good first layer adhesion is to print slow and to try to get the highest possible percentage of the extruded plastic touching the build plate. A very wide flat line works best if your build plate is level. If not so level, you want it a bit high but also very wide. A thin line that's high will have very poor adhesion. The closer your line gets to a tube shape when extruded, the worse the adhesion. You don't want a tube shape. You want it wide. The wider the better.

With some types of plastic filament like polypropylene, that have extreme warping forces, a raft is sometimes needed. But with filament like PETG, or PLA that doesn't suffer from warping problems, I pretty much never use a raft. Usually, if I have problems with parts not sticking, I use First Layer Speed at 15-20%, and First Layer Width at 200-300%. This usually works just as well as a raft. If I'm printing lower than 0.30mm layer height, then I also set First Layer Height to 150-200%.

Since I've started printing on PEI, I pretty much never have problems with parts not sticking. PEI is fantastic.